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How thick should the Mortar Bed for a Shower Pan Floor in a Shower?
QUESTION
When you are pouring you mortar for on your shower pan how thick do you want it before laying of tileANSWER
ANSWER - First of all, the way you construct a shower pan is to first apply a pre-sloped mortar bed to establish a slope to the drain of 1/4" per foot. You can float over a concrete substrate or nail on metal lath over a wood subfloor. Then you have to waterproof the pre-sloped mortar bed with either a liquid applied membrane or a sheet membrane. Then you float a dry-packed mortar bed over the pre-sloped membrane to a thickness of at least 1.5" thick. The mortar bed should have wire reinforcement fabric suspended within the mortar bed if it is a shower pan area larger than 65 square feet. Otherwise you can leave off the wire reinforcement. Per ANSI A108.1A-2017. So after installing the tile the slope to drain should be a minimum of 1/4" per foot, but should not exceed 1/2" per foot per the IAMPO plumbing code IAPMO PS 10612015e1.11 thoughts on “How thick should the Mortar Bed for a Shower Pan Floor in a Shower?”
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I think our shower tile guy made this base too thick. Seems like 2-3 inches. We have to step up to go in shower!!!
It is normal to have a shower curb/dam. It is going to be 4″ tall or so from the bathroom floor. Although curbless showers that were originally meant for handicap showers has become more popular and more in demand.
2 inches of shower pan is not excessive if it’s an old school dry pack with a Pre slope.
Minimum depth of a mud set shower over concrete on a steel pan deck using a max 2″ threshold to meet ADA?
ADA (Americans with Disabilities Act) requires a curbless shower so that it can be accessed with a wheel chair.
So depending on whether the shower is constructed on a concrete substrate on-grade or over a subfloor with floor joists, and the configuration of the shower assembly the thickness of the mortar bed can vary. Non-bonded reinforced mortar beds are recommended at a uniform minimum of 1/25″ and bonded mortar beds can vary from a feather edge to multiple inches thick. Regardless of the thickness, it has to be mixed and installed appropriately.
How thick should mortar bed be at the drain if the mortar bed is sloping down to drain over flat substrate? can it be smaller than 1.5″ at the drain?
If you are installing an unbonded wire reinforced mortar bed per TCNA TR40-23, the mortar bed should be a uniform 1″ to 1.75″ thick, but it should be installed over a pre-sloped primary waterproof membrane. That means that the wood or mortar base under the waterproof membrane has to be sloped to the drain at 1/4″ per foot. The weep holes around the drain where the membrane clamps, must be protected with a weep protector that can be a plastic weep hole protector or pea gravel. We always also recommend to install a liquid applied waterproof membrane over the mortar bed to keep water out and to bond the tile to the membrane. You then need to fill all of the transition joints with an ASTM C920 sealant caulking such as a structural silicone or a polyurethane sealant.
If you have a concrete base you can install a bonded mortar bed to the concrete and then the mortar bed doesn’t have to be a uniform thickness. You can slope the mortar bed from thick to thin, depending on the type of mortar you use. Using a polymer modified mortar allows you to slope from thick to thin. You would then waterproof the mortar bed. You can use a standard two part drain per TCNA B421C-23 or an integrated bonding flange drain per TCNA B422C-23.
We had our shower tile redone and the installer is telling me with the floor being concrete it does not need to be sealed .
All shower pan floors need to be waterproofed if that is what you mean by being sealed. This is a requirement by the international plumbing code and per industry standards.
If you are asking if the concrete slab has to be sealed with a sealer prior to waterproofing, then it that case the answer is no. It does have to be properly prepared for the intended application.
I am installing a pan with preslope, liner then mortar bed and finally tile. My floor turns out is not level and slopes away from the drain. I need to have a thicker preslope at the curb and really need to feather it out as you get to the drain. What type of cement would you use for the preslope. It will be real thin at the drain. I need to make up about an inch of sub floor slope. Would thin-set work? Thanks for your input. Bill
Assuming that you have a structurally sound substrate to bond to, there polymer modified mortars known as patching mortars or fortified mortar beds that you can apply from several inches thick down to a feather edge. They normally require exterior grade plywood to go over or a cementitious base material.
You then need to apply your waterproof liner over that and tie it into the two part drain for clamping, and to transition it up the wall at least 12 inches. You then can float your mortar bed on top of that in a uniform thickness. We also apply a liquid applied waterproof/crack isolation membrane on top of the mortar bed to keep the water out of the mortar so most of the water evacuates into the surface drain. This gives added crack isolation protection as well as a good secondary waterproof membrane.
The ANSI A118.4 and A118.15 clearly state never use thinset to adjust a subfloor. It is not designed for that.